الفهرس 
Introduction.Only 14 pages are availabe for public view
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Abstract
Nowadays, there is an increasing demand by most of the people to retain their teeth whatever their state.
Post treatment endodontic disease is commonly faced by clinicians where they have to clearly understand its causes and how to correctly manage. Failed root canal treatment is mainly due to microbes whether they are persistent or reintroduced ones
Understanding the virulence factors of microbes is very important to be able to counteract these factors and increase our clinical success rate. Microbial biofilm is one of the most effective virulence factors produced by different types of microbes and proved to be one of the most common causes of microbial resistance toward different disinfecting agents used during endodontic treatment. Enterococcus faecalis species is one of the most biofilm forming bacteria.
Introduction of nanotechnology into different fields of medicine with its well-known antibacterial effect encouraged us to try it in our field of endodontics.
This study was done to evaluate the effect of some intracanal medicaments in their nanoform either clinically on healing of periapical lesions and postoperative pain related to endodontic retreatment and in vitro by using confocal laser microscope to determine antibacterial properties of theses formulas through calculating percentage of dead bacteria in comparison with others in the regular form.
Patients (n=60) with failed single root canal treated teeth participated in this study and were divided randomly into 3 group; 2 study groups and one positive control group according to the medicament used.
Preoperative CBCT was done and lesion size was calculated in Cm3. In the first visit, teeth were isolated, old filling was removed, then complete cleaning and shaping was done then one of the medicaments according to the randomization table was applied for one week. Patients were instructed to rate their post-operative pain on specific intervals after the first visit. In the second visit, teeth were isolated, medicament was removed and teeth were obturated.
Follow up after 12 months was done using CBCT to determine lesion size difference and assess healing process.
Extracted teeth samples were collected and prepared to the same apical size and taper and autoclaving at 121o C for 20 minutes. Enterococcus faecalis was inoculated into samples for 21 days then they were divided into 5 groups according to intracanal medicament used. Following treatment samples were sectioned and scanned under confocal laser scanning microscope to detect the percentage of dead bacteria.
The results of this study showed that there was no significant difference in healing and postoperative pain after using the different intracanal medicaments, while the two new nano formulas showed better results in their antibacterial properties.
This study concluded that new nano trends of intracanal medicaments can be used in cases with failed root canal treatment to help decrease bacterial load along the root canal which has a positive influence on healing process. Further combinations with other medicament may show better effect and enhance the treatment outcome.
Within the limitation of this study, the following conclusions can be withdrawn:
1. Irrigation with sodium hypochlorite remains an integral step in root canal retreatment for its antibacterial and antibiofilm effects.
2. Clinical outcomes in terms of healing and postoperative pain of calcium hydroxide with nano silver and nano Chitosan were comparable to that of conventional calcium hydroxide intracanal medicament with a little with a faster pain reduction in nano medicaments groups.
3. Complete removal of bacterial from root canal system is impossible, while nano based intracanal medicaments showed promising results in this field.
Recommendations:
• Further studies with different formulas and combinations and longer follow up periods can be performed.